Switching post-menopausal women with oestrogen receptor-positive early breast cancer to the drug exemestane (Aromasin) after two to three years of tamoxifen improves long-term survival, a study claims.
This is compared to a continuation of tamoxifen to the full five years.
The research, published in the Journal of Clinical Oncology, involved 4,724 postmenopausal women from 37 countries.
It found that five years after completing treatment, the relative risk reduction for women who received exemestane meant they were 18% less likely to have disease recurrence – translating to a 4.5% absolute risk reduction at eight years.
Furthermore, women who received exemestane were 14% less likely to die than those who stayed on tamoxifen, equivalent to an absolute difference in survival of 2.4% at eight years.
No significant differences were found between the treatment groups in cases of long-term side effects in the post treatment period.
Professor Coombes, Head of Division of Cancer at Imperial College, and the lead investigator of the study, claimed the study provided "encouraging news" for people with early stage breast cancer.
"The findings confirm that the strategy of switching to exemestane mid-way through the five-year tamoxifen treatment plan provides a clear and durable benefit for relapse and overall survival," said Professor Coombes.
"Previous analysis, based on a shorter follow-up, had shown a clear relapse advantage but until these study results, the magnitude and duration of the overall survival benefit had been uncertain.
"The 91-month results show that the relapse improvement does not seem to diminish over time and have clarified that the survival advantage is robust and enduring".